Is this my guitar or my set up guy?

About two months ago I purchased an American Special Strat from Guitar Center. After purchasing it i took it to a local music store to get it set up because there was some fret buzzing. When it came back it sounded fine. A week ago I changed the strings. I did it correctly and did not move the saddles. The strings were also the same gauge. However, the buzzing is back and worse. What I am wondering is if this is my guitar or the guy who set it up. Hopefully I can return it if it is the guitar. Thanks